Synthetic polymeric textiles, e.g., polyester textiles, are commonly used in a wide variety of consumer and industrial applications. These polyester fabrics are predominantly copolymers of ethylene glycol and terephthalic acid, and are sold under a number of trade names, e.g., Dacron.RTM., Fortrel.RTM., Kodel.RTM. and Blue C Polyester.RTM.. One disadvantage of polyester textiles is the difficulty in removing oily residues, i.e., naphthenic, aliphatic or alkane hydrocarbon residues, such as motor oil, tar, pitch, lubricating oil or the like, from the material once it has been soiled with such residues. This is in part due to the hydrophobic nature of the polyester textile which makes the material difficult to wet with aqueous solutions of laundering detergents.
As a result, soil release compositions have been developed for application to polyester textiles. These soil release compositions, which are typically comprised of non-fiber forming polyether-polyester copolymers, impart soil release properties by modifying the polyester textile surface to enable release and removal of oily residues from the polyester textile using conventional aqueous laundering techniques. Typical polymeric soil release compositions are described in various U.S. patents, e.g., U.S. Pat. No. 3,416,952.
To impart anti-wrinkle properties and to control dimensional stability, e.g., shrinkage, of polyester textiles, the textile is thermally treated or heat set. Heat setting aligns the crystal morphology of the polyester fibers to a more parallel rather than random orientation. In modern polyester textile processing mills, heat setting is typically effected at a temperature of at least about 375.degree. F. (191.degree. C.) to speed throughput and to better control fabric shrinkage. Such temperatures may range up to about 405.degree. F. (207.degree. C.) or so. Since the soil release composition is applied to the polyester textile prior to heat setting, an antioxidant is often included in the soil release composition to retard or prevent thermal degradation of the soil release composition during the heat setting step.
As disclosed in the above-mentioned U.S. Pat. No. 3,416,952, antioxidant materials typically used to impart thermal stability to the polymeric soil release compositions described therein include sterically hindered phenols, aromatic amines and organic sulfur compounds. However, none of the antioxidant materials specifically disclosed therein satisfactorily retard or prevent thermal degradation of the polymeric soil release composition at polyester textile heat set temperatures of about 375.degree. F. (191.degree. C.). As a result, polyester textiles finished with such soil release compositions and heat set at such elevated temperatures have unsatisfactory soil release properties resulting in incomplete removal of oil residues from the textile when using conventional aqueous laundering techniques.